This invention relates generally to the patterning of photoresist.
Photoresist may be utilized to transfer a pattern from a mask to a semiconductor wafer in a repeatable fashion. Generally the process of photolithography involves a few basic steps. Initially, a photoresist is formed on top of the wafer by a spin-on process. Excess solvent is then removed in a pre-exposure bake. Thereafter, certain regions on the wafer are selectively exposed to radiation. Next, the wafer is baked in the so-called post-exposure bake. Then the wafer and, particularly, the photoresist is developed and rinsed. Regions that are exposed may either be resistant to removal or may be more prone to removal so that the pattern of a mask is transferred to the wafer in a repeatable fashion.
The quality of the pattern that is transferred from the photoresist to the underlying layer is based at least in part on what is call line edge roughness. The rougher the resulting lines transferred to the photoresist, the rougher the transfer in the pattern to the semiconductor wafer, which in turn may impact the performance of the device under fabrication.
Thus, it would be desirable to reduce the line edge roughness of the photoresist.